docs: fill out compat, lvglh, and toolchain documentation

Replace placeholder content in doc/compat/, doc/lvglh/, and
doc/toolchain/ with comprehensive documentation derived from the
source files.

- compat: document Wasuro WASM VM compatibility shims
- lvglh: document LVGL v9.2.2 configuration, fonts, and patches
- toolchain: document all 13 build pipeline scripts

doc/toolchain/compile_link.md

@@ -1 +1,47 @@
-# Placeholder
+# compile_link.sh
+
+Links all object files and libraries into the final kernel binary.
+
+## Overview
+
+`compile_link.sh` collects every `.o` object file in `lib/`, locates `libgcc` for i386, and invokes the GNU linker (`ld`) to produce `bin/kernel.bin`. The linker script `toolchain/linker.script` controls the memory layout of the resulting binary.
+
+## Prerequisites
+
+- `ld` (GNU linker) and `gcc` must be available.
+- All object files must have been produced by prior build steps (`compile_stub.sh`, `compile_sources.sh`).
+- `lib/liblvgl.a` must exist (produced by `compile_lvgl.sh`).
+- `toolchain/linker.script` must exist.
+- The `bin/` output directory must exist.
+
+## Inputs
+
+| Source | Description |
+|--------|-------------|
+| `lib/*.o` | All ELF object files (boot stub, Pascal units, splash screen, etc.). |
+| `lib/liblvgl.a` | Static LVGL library archive. |
+| `libgcc` (system) | GCC runtime support library for i386, located via `gcc -m32 -print-libgcc-file-name`. |
+| `toolchain/linker.script` | Linker script defining section layout and entry point. |
+
+## Outputs
+
+| File | Description |
+|------|-------------|
+| `bin/kernel.bin` | The final linked, stripped kernel binary. |
+
+## Behavior
+
+1. Collects all `.o` files from `lib/`, excluding `lib/stub.o` from the general list.
+2. Prepends `lib/stub.o` to the front of the object list so the boot entry point is linked first.
+3. Locates `libgcc` for the 32-bit target using `gcc -m32 -print-libgcc-file-name`.
+4. Invokes `ld` with the following flags:
+   - `-m elf_i386` -- Target i386 ELF format.
+   - `-s` -- Strip all symbol information.
+   - `--gc-sections` -- Remove unused sections (works with FPC's `-CX -XXs` smart-linking).
+   - `-T toolchain/linker.script` -- Use the project linker script.
+   - `--start-group` / `--end-group` -- Wraps `liblvgl.a` and `libgcc` to resolve circular references between them.
+
+## Notes
+
+- `stub.o` must be first in the link order because it contains the multiboot header and the initial entry point that GRUB transfers control to.
+- The `--start-group` / `--end-group` construct allows the linker to iterate over `liblvgl.a` and `libgcc` multiple times to resolve all symbols, which is necessary when C library objects have mutual dependencies.